Troubleshooting professional audio circuits requires an assortment of test equipment. In the field of audio/video production, those responsible for setting up and maintaining systems are often required to carry the test equipment. The assortment of test equipment may include a variety of separate testing and troubleshooting devices, such as, for example, tone generators, portable audio amplifiers, and voltage metering devices. Typically, one carries a large “listen box” and several other tools that are cumbersome to carry.